Right now, ZTE Axon 7 Mini handsets in the US have one of three possible software builds, but soon all will get the same "Build 21" firmware. This update promises to bring new APN settings for all major carriers, HD Voice call on T-Mobile, and more.
http://www.notebookcheck.net/ZTE-Axon-7-Mini-to-get-unified-software-update.191497.0.html
Any news on European updates. I'm still on build 2 after a month!